1. Field of the Invention
This invention pertains to tethered aerial tops.
2. Description of the Related Art
Aerial tops, colloquially known as yo-yos, generally consist of body halves separated by an intermediate axle. A tether encircles, and extends from, the axle for coupling the yo-yo to a user""s hand, imparting rotational motion to the top, and general control of the yo-yo. As is known, the body halves are generally thick, circular discs having a diameter in the range of four to ten centimeters, but more commonly in the range of five to six centimeters. The discs are commonly one to two centimeters thick. The discs are coupled to the axle so as to be separated from one-another by one-half to one centimeter. The tether is commonly a cord of twisted strands about 42 inches (1.07 m) in length and includes a looped end that encircles the yo-yo axle.
In operation, the tether is wound onto the axle and coupled to a user""s finger. The user then throws the yo-yo downward and away from the user""s body and the restraint force of the tether causes the yo-yo to rotate as it moves away from the user""s hand and unwinds the tether. With proper technique, the yo-yo can be made to spin freely when it reaches the end of the tether, a method known in the art as making the yo-yo xe2x80x9csleep.xe2x80x9d
Many tricks can be performed while the yo-yo is sleeping. As a result, a yo-yo that can be made to sleep a long time is preferable over a yo-yo that sleeps a relatively shorter time. Several factors affect the sleep time of a yo-yo: the yo-yo""s rate of rotation when it reaches the end of the tether, it""s moment of inertia, and friction. Friction has several components, including the friction of the string on the axle and air resistance of the rotating body. Thus, sleep time can be increased by increasing the rate of rotation, increasing the moment of inertia (without slowing the rotation rate), or decreasing overall friction.
In Ennis, U.S. Pat. No. 4,130,962, the weight of the yo-yo discs are concentrated in the periphery of the discs to increase the yo-yo""s moment of inertia. A rotating body with a high moment of inertia will spin longer than a similar body with a smaller moment of inertia, assuming both have the same initial rate of rotation. Thus, Ennis provides the yo-yo with a relatively large moment of inertia by placing the weight of the yo-yo near the periphery of the body discs.
Caffrey, U.S. Pat. No. 4,332,102, provides a yo-yo with reduced frictional drag between the yo-yo tether and the axle by attaching the tether to a bearing-pulley located around the axle. Placing a bearing between the tether and the axle increases the spinning time of the yo-yo by decreasing friction. In order to provide the user with a means to retrieve the yo-yo, that is, cause the yo-yo to grab the string and use its rotational momentum to wind itself onto the tether, the invention provides centrifugally operated clutches that engage the sides of the bearing-pulley and the clutches engage the bearing-pulley as the yo-yo""s rotational speed falls below a predetermined speed.
Thus, it is apparent there is a desire to enhanced a time of free spinning to perform yo-yo tricks and to better enjoy the toy.
The present invention improves upon the prior art by providing an aerial top having a stepped axle that extends between first and second body portions and a tether having a varied diameter along its length. The stepped axle includes distal end portions with a first diameter and a central portion with a second, smaller diameter. The end portions are separated from the central portion by annular sidewalls. The tether is coupled to the central portion of the stepped axle and includes a loop for connection to a user""s finger at its other end.
Preferably, the annular walls between the axle end and central portions are substantially orthogonal to surfaces of the axle end and central portions, respectively. Alternatively, the annular sidewalls may be oblique to the axle portion surfaces.
In preferred embodiments, the tether is a cord having different portions of different diameters. A portion with a smallest diameter is located nearest the yo-yo, and a portion with a largest diameter is located furthest from the yo-yo. In an alternative embodiment, the tether is tapered from a relatively large diameter to a relatively smaller diameter at a tether end that is coupled to the yo-yo.
In preferred operation, the tether is wound onto the axle such that the thinnest diameter tether portion is wound onto the axle central portion and the larger diameter tether portion is wound onto the axle end portions. Thus, taking advantage of an increased moment arm due to the large diameter axle end portions, and conservation of angular momentum, the yo-yo of the present invention provides advantages over the prior art.